354204061c
This PR shows that GDB can easily trigger an assertion here, in
infrun.c:
5392 /* Did we find the stepping thread? */
5393 if (tp->control.step_range_end)
5394 {
5395 /* Yep. There should only one though. */
5396 gdb_assert (stepping_thread == NULL);
5397
5398 /* The event thread is handled at the top, before we
5399 enter this loop. */
5400 gdb_assert (tp != ecs->event_thread);
5401
5402 /* If some thread other than the event thread is
5403 stepping, then scheduler locking can't be in effect,
5404 otherwise we wouldn't have resumed the current event
5405 thread in the first place. */
5406 gdb_assert (!schedlock_applies (currently_stepping (tp)));
5407
5408 stepping_thread = tp;
5409 }
Like:
gdb/infrun.c:5406: internal-error: switch_back_to_stepped_thread: Assertion `!schedlock_applies (1)' failed.
The way the assertion is written is assuming that with schedlock=step
we'll always leave threads other than the one with the stepping range
locked, while that's not true with the "next" command. With schedlock
"step", other threads still run unlocked when "next" detects a
function call and steps over it. Whether that makes sense or not,
still, it's documented that way in the manual. If another thread hits
an event that doesn't cause a stop while the nexting thread steps over
a function call, we'll get here and fail the assertion.
The fix is just to adjust the assertion. Even though we found the
stepping thread, we'll still step-over the breakpoint that just
triggered correctly.
Surprisingly, gdb.threads/schedlock.exp doesn't have any test that
steps over a function call. This commits fixes that. This ensures
that "next" doesn't switch focus to another thread, and checks whether
other threads run locked or not, depending on scheduler locking mode
and command. There's a lot of duplication in that file that this ends
cleaning up. There's more that could be cleaned up, but that would
end up an unrelated change, best done separately.
This new coverage in schedlock.exp happens to trigger the internal
error in question, like so:
FAIL: gdb.threads/schedlock.exp: schedlock=step: cmd=next: call_function=1: next to increment (1) (GDB internal error)
FAIL: gdb.threads/schedlock.exp: schedlock=step: cmd=next: call_function=1: next to increment (3) (GDB internal error)
FAIL: gdb.threads/schedlock.exp: schedlock=step: cmd=next: call_function=1: next to increment (5) (GDB internal error)
FAIL: gdb.threads/schedlock.exp: schedlock=step: cmd=next: call_function=1: next to increment (7) (GDB internal error)
FAIL: gdb.threads/schedlock.exp: schedlock=step: cmd=next: call_function=1: next to increment (9) (GDB internal error)
FAIL: gdb.threads/schedlock.exp: schedlock=step: cmd=next: call_function=1: next does not change thread (switched to thread 0)
FAIL: gdb.threads/schedlock.exp: schedlock=step: cmd=next: call_function=1: current thread advanced - unlocked (wrong amount)
That's because we have more than one thread running the same loop, and
while one thread is stepping over a function call, the other thread
hits the step-resume breakpoint of the first, which needs to be
stepped over, and we end up in switch_back_to_stepped_thread exactly
in the problem case.
I think a simpler and more directed test is also useful, to not rely
on internal breakpoint magics. So this commit also adds a test that
has a thread trip on a conditional breakpoint that doesn't cause a
user-visible stop while another thread is stepping over a call. That
currently fails like this:
FAIL: gdb.threads/next-bp-other-thread.exp: schedlock=step: next over function call (GDB internal error)
Tested on x86_64 Fedora 20.
gdb/
2014-10-29 Pedro Alves <palves@redhat.com>
PR gdb/17408
* infrun.c (switch_back_to_stepped_thread): Use currently_stepping
instead of assuming a thread with a stepping range is always
stepping.
gdb/testsuite/
2014-10-29 Pedro Alves <palves@redhat.com>
PR gdb/17408
* gdb.threads/schedlock.c (some_function): New function.
(call_function): New global.
(MAYBE_CALL_SOME_FUNCTION): New macro.
(thread_function): Call it.
* gdb.threads/schedlock.exp (get_args): Add description parameter,
and use it instead of a global counter. Adjust all callers.
(get_current_thread): Use "find current thread" for test message
here rather than having all callers pass down the same string.
(goto_loop): New procedure, factored out from ...
(my_continue): ... this.
(step_ten_loops): Change parameter from test message to command to
use. Adjust.
(list_count): Delete global.
(check_result): New procedure, factored out from duplicate top
level code.
(continue tests): Wrap in with_test_prefix.
(test_step): New procedure, factored out from duplicate top level
code.
(top level): Test "step" in combination with all scheduler-locking
modes. Test "next" in combination with all scheduler-locking
modes, and in combination with stepping over a function call or
not.
* gdb.threads/next-bp-other-thread.c: New file.
* gdb.threads/next-bp-other-thread.exp: New file.
54 lines
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54 lines
1.9 KiB
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# Copyright (C) 2014 Free Software Foundation, Inc.
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# This program is free software; you can redistribute it and/or modify
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# it under the terms of the GNU General Public License as published by
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# the Free Software Foundation; either version 3 of the License, or
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# (at your option) any later version.
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#
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# This program is distributed in the hope that it will be useful,
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# but WITHOUT ANY WARRANTY; without even the implied warranty of
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# MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
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# GNU General Public License for more details.
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#
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# You should have received a copy of the GNU General Public License
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# along with this program. If not, see <http://www.gnu.org/licenses/>.
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# Test that GDB behaves correctly when a "next" steps over a call, and
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# another thread hits a breakpoint that doesn't cause a user visible
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# stop (and so needs to be stepped over). GDB used to trip on an
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# invalid assertion - PR17408.
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standard_testfile
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if {[prepare_for_testing "failed to prepare" $testfile $srcfile {debug pthreads}] == -1} {
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return -1
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}
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# Test all "set scheduler-locking" variants.
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foreach schedlock {"off" "step" "on" } {
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with_test_prefix "schedlock=$schedlock" {
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clean_restart $binfile
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if ![runto_main] {
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continue
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}
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gdb_breakpoint [gdb_get_line_number "set wait-thread breakpoint here"]
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gdb_continue_to_breakpoint "run to wait-thread breakpoint"
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gdb_test "info threads" "2 .*\\\* 1.*" "info threads shows all threads"
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delete_breakpoints
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gdb_breakpoint [gdb_get_line_number "set breakpoint child here"]
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# Give it a condition that always fails.
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gdb_test "condition \$bpnum global_zero == 1" ".*"
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gdb_test_no_output "set scheduler-locking $schedlock"
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# While stepping over the sleep call, the other thread hits a
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# breakpoint that doesn't cause a user visible stop (and so
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# needs to be stepped over). The next should complete as if
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# that breakpoint never triggered.
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gdb_test "next" "EXIT_SUCCESS.*" "next over function call"
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}
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}
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